2026-04-02
Insulation Testing: Using the XHMR-5000V Insulation Resistance Tester, the insulation of Phase C was measured at 0.08 MΩ, with a residual voltage of 468 V. For Phases A and B, the insulation values reached the GΩ range within 15 seconds, which was deemed normal. Preliminary Conclusion: Phase C exhibits a main insulation fault.
Total Length Verification: First, using the XHGG502 Cable Fault Tester, the total length of the cable was measured—via the low-voltage pulse method—to be approximately 6400.9 meters; this figure is essentially consistent with the cable length known at the site.
The High-Voltage Flashover Method, utilizing the XHGG502 Cable Fault Tester, was employed to determine the fault distance on Phase C. Using an XHYB-5/50 Test Transformer in conjunction with an XHCC-6/40 Pulse Energy Storage Capacitor, the fault point broke down as the voltage rose to 14 kV, yielding a standard flashover waveform. Based on waveform analysis, the fault point is located approximately 1694.5 meters from the testing terminal.
Based on the technical drawings, the on-site personnel identified the cable route in the vicinity of the 1694.5-meter mark. To amplify the discharge sound and facilitate precise pinpointing, the technicians raised the voltage to approximately 23 kV; they then proceeded along the route using an XHDD503E cable fault pinpointing device to conduct simultaneous acoustic-magnetic tracing. The discharge sound was exceptionally loud—clearly audible and easily distinguishable in the open air. Following the sound, the team quickly pinpointed the exact location of the fault, completing the localization process with high efficiency and accuracy.
Excavation has confirmed that the fault location lies beneath a newly constructed drainage ditch situated directly above the cable. During construction, while workers were erecting steel reinforcement formwork, a steel bar pierced directly into the cable—penetrating its insulation layer—resulting in a phase-to-ground fault on Phase C. The results of the excavation align perfectly with the diagnostic localization, establishing the cause of the fault clearly and unequivocally.
